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Warm Up Simplify each radical. 1. 2. 3. Find the distance between each pair of points. Write your answer in simplest radical form. 4. C (1, 6) and D ( – 2, 0) 5. E (–7, –1) and F (–1, –5).
E N D
Warm Up Simplify each radical. 1.2.3. Find the distance between each pair of points. Write your answer in simplest radical form. 4. C (1, 6) and D (–2, 0) 5.E(–7, –1) and F(–1, –5)
A dilationis a transformation that changes the size of a figure but not its shape. The preimage and the image are always similar. A scale factordescribes how much the figure is enlarged or reduced. For a dilation with scale factor k, you can find the image of a point by multiplying each coordinate by k: (a, b) (ka, kb).
Helpful Hint If the scale factor of a dilation is greater than 1 (k > 1), it is an enlargement. If the scale factor is less than 1 (k < 1), it is a reduction.
Draw the border of the photo after a dilation with scale factor Example 1: Computer Graphics Application
Step 1 Multiply the vertices of the photo A(0, 0), B(0, 4), C(3, 4), and D(3, 0) by Example 1 Continued Rectangle ABCD Rectangle A’B’C’D’
Example 1 Continued Step 2 Plot points A’(0, 0), B’(0, 10), C’(7.5, 10), and D’(7.5, 0). Draw the rectangle.
What if…?Draw the border of the original photo after a dilation with scale factor Check It Out! Example 1
Step 1 Multiply the vertices of the photo A(0, 0), B(0, 4), C(3, 4), and D(3, 0) by Check It Out! Example 1 Continued Rectangle ABCD Rectangle A’B’C’D’
B’ C’ 2 0 1.5 A’ D’ Check It Out! Example 1 Continued Step 2 Plot points A’(0, 0), B’(0, 2), C’(1.5, 2), and D’(1.5, 0). Draw the rectangle.
Example 2: Finding Coordinates of Similar Triangle Given that ∆TUO ~ ∆RSO, find the coordinates of U and the scale factor. Since ∆TUO ~ ∆RSO, Substitute 12 for RO, 9 for TO, and 16 for OY. 12OU = 144 Cross Products Prop. OU = 12 Divide both sides by 12.
So the scale factor is Example 2 Continued U lies on the y-axis, so its x-coordinate is 0. Since OU = 12, its y-coordinate must be 12. The coordinates of U are (0, 12).
Check It Out! Example 2 Given that ∆MON ~ ∆POQ and coordinates P (–15, 0), M(–10, 0), and Q(0, –30), find the coordinates of N and the scale factor. Since ∆MON ~ ∆POQ, Substitute 10 for OM, 15 for OP, and 30 for OQ. 15 ON = 300 Cross Products Prop. ON = 20 Divide both sides by 15.
So the scale factor is Check It Out! Example 2 Continued N lies on the y-axis, so its x-coordinate is 0. Since ON = 20, its y-coordinate must be –20. The coordinates of N are (0, –20).
Example 4: Using the SSS Similarity Theorem Graph the image of ∆ABC after a dilation with scale factor Verify that ∆A'B'C' ~ ∆ABC.
Step 1 Multiply each coordinate by to find the coordinates of the vertices of ∆A’B’C’. Example 4 Continued
Example 4 Continued Step 2 Graph ∆A’B’C’. B’ (2, 4) A’ (0, 2) C’ (4, 0)
Lesson Quiz: Part I 1. Given X(0, 2), Y(–2, 2), and Z(–2, 0), find the coordinates of X', Y, and Z' after a dilation with scale factor –4. 2. ∆JOK ~ ∆LOM. Find the coordinates of M and the scale factor. X'(0, –8); Y'(8, –8); Z'(8, 0)